The objective of this proposal is to study the two-stage model of carcinogenesis in the cervico-vaginal epithelium of mice. Since the cervico-vaginal epithelium (CVE) shares many characteristics with the epidermis but involves ovarian hormones in the regulation of both cell proliferation and differentiation, it appears to be a unique model to study the role of ovarian hormones in tumor initiation and promotion. The long term goals of the project will be to study possible mechanisms by which hormones may regulate different stages of chemical carcinogenesis. The main hypothesis of this project is that estrogens will act as promoters in this system. Preliminary experiments have shown that squamous cell carcinomas can be induced in chemically initiated animals promoted with either TPA or estrogens. This proposal will be oriented to confirm these preliminary results and to investigate possible mechanisms of promotion in this organ. Mice initiated with 10 or 50 nmol of dimethylbenzantracene (DMBA) will be promoted with different doses of 17 beta-estradiol (E2) using subcutaneous silastic tubing. In a separate experiment, synthetic estrogens will also be assayed. Tumors induced by these protocols will be characterized for the following parameters: hormone dependence, keratin pattern, chromosomal constitution and activation of the Ha-ras gene. Other aims of this proposal will be to define the nature of premalignant lesions in this system and characterize those lesions. In order to study possible mechanisms of promotion, a culture of initiated VE cells will be produced by transferring either an activated Ha-ras gene or HPV-16 DNA. The effect of ovarian hormones on these genetic altered cultures will be evaluated in short term and long term experiments in vivo and in vitro.